Anticonvulsants during pregnancy: a danger to the developing fetus?

Antiepileptic drugs are endocrine disruptors for the human fetal testis ex vivo

Valproic acid (VPA) has long been the most widely used antiepileptic drug (AED) for the treatment of epilepsy, bipolar psychiatric disorders, and migraine. However, long-term VPA treatment has several adverse effects on the male reproductive system notably on endocrine functions and/or spermatic parameters. In utero exposure of the fetus to VPA is well known to be associated with a higher risk of several congenital malformations including those of male reproductive organs. Subsequent generations of AEDs, such as carbamazepine (CARB) and lamotrigine (LAM), are considered safer and are currently recommended for women of child-bearing age with epilepsy. Because anomalies of the male genital tract mostly result from endocrine imbalance during fetal life, we hypothesized that AEDs could directly impair testis differentiation. We thus aimed at identifying and characterizing the effects of VPA, CARB, and LAM on the differentiation and function of the different testicular cell types, and at understanding the mechanisms underlying these effects. By using ex vivo culture of first-trimester human fetal testes, we show that VPA induces multiple endocrine disruptive effects, compared with the milder ones caused by CARB and LAM. AED also subtly altered the germ cell lineage in distinct manners. Transcriptomic analysis of VPA-induced alterations highlighted a very broad range of effects on the fetal testis. Overall, our results show that AEDs can behave as endocrine disruptors for the human fetal testis ex vivo. This is consistent with, and likely underlies, the VPA-induced male genital tract masculinization abnormalities observed in patients.

Embryonic arrhythmia by inhibition of HERG channels: a common hypoxia-related teratogenic mechanism for antiepileptic drugs?

PURPOSE

There is evidence that drug-induced embryonic arrhythmia initiates phenytoin (PHT) teratogenicity. The arrhythmia, which links to the potential of PHT to inhibit a specific potassium channel (Ikr), may result in episodes of embryonic ischemia and generation of reactive oxygen species (ROS) at reperfusion. This study sought to determine whether the proposed mechanism might be relevant for the teratogenic antiepileptic drug trimethadione (TMO).

METHODS

Effects on embryonic heart rhythm during various stages of organogenesis were examined in CD-1 mice after maternal administration (125-1,000 mg/kg) of dimethadione (DMO), the pharmacologically active metabolite of TMO. Palatal development was examined after administration of a teratogenic dose of DMO and after simultaneous treatment with DMO and a ROS-capturing agent (alpha-phenyl-N-tert-butyl-nitrone; PBN). The Ikr blocking potentials of TMO and DMO were investigated in HERG-transfected cells by using voltage patch-clamping tests.

RESULTS

DMO caused stage-specific (gestation days 9-13 only) and dose-dependent embryonic bradycardia and arrhythmia at clinically relevant maternal plasma concentrations (3-11 mM). Hemorrhage in the nasopharyngeal part of the embryonic palate (within 24 h) preceded cleft palate in fetuses at term. Simultaneous treatment with PBN significantly reduced the incidence of DMO-induced cleft palate, from 40 to 13%. Voltage patch-clamping studies showed that particularly DMO (70% inhibition), but also TMO, had Ikr blocking potential at clinically relevant concentrations.

CONCLUSIONS

TMO teratogenicity, in the same way as previously shown for PHT, was associated with Ikr-mediated episodes of embryonic cardiac arrhythmia and hypoxia/reoxygenation damage.

Long-lasting effects of early barbiturates on central nervous system and behavior

Forty years of prescribing barbiturates to pregnant women and infants, and thirty years of animal research have shown that barbiturates affect the developing central nervous system (CNS) and behavior. This paper compiles and reviews animal and selected human literature in this research area. Early barbiturate exposure in animals reduces brain weight with related changes in brain biochemistry and neuromorphology. Significant changes may be found in surviving adult offspring. Evidence of CNS and behavioral damage in human beings due to early barbiturate exposure is not clearcut, however, confounded by the conditions for which the drugs are prescribed. In animals, early drug exposure significantly reduces levels of hormones, vitamins, and other biologically active macromolecules via (long-lasting) induction of hepatic metabolizing enzymes. Whether or not in humans treated with barbiturates, hormone levels remain within the normal range (by-feed-back regulation) and, also, if vitamin deficiencies can be simply corrected by supplements is still being debated. Early barbiturates administered to animals is associated with long-lasting disturbances in activity, learning performance, sexual behavior, and reproductive function, but not in a simple dose-exposure related manner. Animal studies show that long-lasting functional tolerance to drugs develops following early barbiturate exposure. Although infants become "passively addicted" following in utero exposure, there is as yet no data on subsequent development of human adult tolerance. Drug related damage must, in any case, be weighed against therapeutic benefits of drug administration and the results of failure to treat.

On aetiological factors in hypospadias

An analysis of genetic and non-genetic factors which might be of importance for the aetiology of hypospadias was performed in a clinical and in a registered material comprising altogether 893 hypospadiacs. Of 213 index patients in the clinical material, the probable aetiology was known in 11: in 3 patients chromosomal aberrations, in 2 well-defined syndromes with a known genetic background, in one maternal diabetes, in 2 maternal rubella, and 2 of the hypospadiacs were born after the mothers' use of anticonvulsant drugs and one after the mother's use of thalidomide. Other hypospadiacs were identified in 28 of the families of the remaining 202 index patients. As regards inheritance, 10 cases of hypospadias associated with clinodactyly were found in one family and this suggests an autosomal dominant gene as the cause of hypospadias. In the great majority (174/213) of index patients neither genetic nor non-genetic factors could be demonstrated but a significant cyclic trend for the month of birth and the month of the last menstrual period was found.

Recurrence risks in a consecutive series of congenitally malformed children dying in the perinatal period

During a 4 1/2-year period a special study of 207 consecutive perinatal deaths, including clinical, genetical, roentgenological and autopsy investigations, was undertaken with the aim of identifying inherited malformations with a high risk of recurrence to subsequent sibs. Fifty-three of the children dying perinatally were malformed. In 13 cases the cause of the malformation was purely genetic; 11 were caused by mutant genes of large effect, and two by chromosomal aberrations. Information from such a study provides a good basis for genetic counselling of the family.

The fetal trimethadione syndrome

Three families are described in which each of the mothers took trimethadione during pregnancy. From a comparison of siblings in each family and of others exposed to trimethadione in utero, a specific phenotype is delineated. Features included in the fetal trimethadione syndrome are developmental delay, speech difficulty, V-shaped eyebrows, epicanthus, low-set ears with anteriorly folded helix, palatal anomaly, and irregular teeth. Additional anomalies in some of the patients include intrauterine growth retardation, short stature, microcephaly, cardiac anomaly, ocular anomaly, hypospadias, inguinal hernia, and simian creases.

Maternal anticonvulsants and perinatal risk

According to data found in the literature, children born to epileptic mothers on anticonvulsant therapy have an increased perinatal mortality rate, namely 2-3 times the average. The congenital malformations attributed to anticonvulsant drugs cannot fully account for this high mortality rate. A case is described in which a severe bleeding disorder manifested itself in successive offspring. A discussion follows in which this defect in blood coagulation in the newborn and the role played by vitamin K is considered as representing an important and preventable cause of neonatal death and morbidity. Other features of the postnatal syndrome (CNS depression, congenital heart disease, withdrawal symptoms, anemia) are mentioned in the case report. Suggested preventative measures employing vitamin K, folic acid and vitamin D are briefly discussed.